The Hero is too important now:
- No not really. My Hero let Flemeth and Morrigan sort out their own mess and just lied to Morrigan. She has no idea that Flemeth is Mytal and would properly not believe so if told. She has zero ties to red lyrium and rifts (which was introduced in da2/da:I and have no knowlegde on Eluvian that another Pc couldn't learn just as quick. (Since it boils Down to - Mirror you can walk through).
As for the Ancient darkspawn magister Things, she would rather avoid them since Corepheus proved able to control tainted mages.
Any political ties is tied to Feraldan and thankfully we are about to leave that country behind. As for the chantry mage, templars? My wardden is just glad to be able to avoid that mess. Also she hates the grey wardens as an organisation. Her lover was Zevran and she killed Leliana and trusted Morrigan to be able to look after herself, so yeah. No ties there.
Few others measure up
That's... just not true. My Hof only special strenght is the taint and the weird blood power from the DLC, other than that she has a good silver tongue, but I doubt that it would move the World.
My Hawke have her beat in sheer determination and my Inqusitor have a Whole orgnaisation and the anchor.
Your Hero has already returned.
Actually with Zev, she has not put her life on hold, zev is with her 
As for what she would do with the cure? Use it on herself and then sent a nice letter to Weishaupt to explain how it works. Then ride of into the sunset and be happy. As far as she has concerned she has done her duty.
Keep your option open
I prefer being left in the dust, thank you. Hawke was my favorite PC and they butchered her for a quest she had no busniness being in and manage to retroactively destory my enjoyment of DA2 which was my favorite game. And Hawke was mine, I had plenty of control over her.
If the Hero comes back it will be as an NCP and that would mean out of my hand.
Varric is right. The Hero has had her happy ending. I am glad to know she is working to preserve it, but I am even happier to move unto the NeXT interesting person. I am not in Dragon Age because of the HoF.
Noble end
I don't have an ultimate sacrifice, but if I did I would want the Fereldans and perhaps the Feraldan Wardens (WHO was the one the hero sacrificed themselves for) to have their grave and honor them,
Everything we know about the Weishaupt wardens is that they are not good persons, and I certainly would want the people the hof sacrificed themselves for to be one remembering them, not the corrupt, shady head of an orgnanisation who the hero never met and who would properly misuse their name.
And there are tiles for that in Keep. You probably already filled them out. So those choices would be accurately reflected in the next installment. Also, your Hero did Witch Hunt, which means they learned things about scrying, Elini Zinovia, the eluvians, the Lights of Arlathan, and so on. But this isn't the thread to talk about what makes the Hero tie into future storylines.
Fine, so have your Hero avoid them. No ties? Fine. Have a nice life. Oh, and you may want to let BioWare know this, cuz, ya know... they don't know any of that and probably have something else in mind.
I'm talking about skills and abilities.
Actually Zev isn't with her. DA:I saw to that. No, Zev is off being an assassin and helping the Inquisition in a distant capacity. And your Hero is searching for the cure. Her and Zev... split up. Perhaps forever... unless you join our cause. Because as of now, this isn't about her concerns, it's about BioWare's.
Oh you prefer to be left in the dust eh? Okay great. Next game, your Hero returns to Weisshaupt, because sending a letter is too risky, and she is thusly slain upon return by whatever evil force doesn't want the Wardens to be cured. Zevran commits suicide out of grief. Have a nice day, duster. 
Yes, they butchered your Hawke. Why? Because you had no say in the matter. So you've seen where that road leads. Wouldn't you rather have a say in your Hero's fate lest she meet the same chopping block?
She didn't have her happy ending. She's searching for the cure, whether you wanted her to or not. What does BioWare have in store for her next?
Well too bad. Ferleden doesn't host the Hero's tomb, Weisshaupt does. That is explained in Origins, actually.
Bottom line, if you don't want BioWare screwing up your Hero like they did your Champion, support the movement to bring the Hero back and place the Hero back in the hands of the player.